Shaped charges are well-known in the petroleum industry and are used to perforate a casing and the surrounding producing formations in a bore hole. The shaped charges are required to be attached in some fashion to a charge carrier and held in position while lowered into the bore hole casing and positioned for firing. It is generally well-known that once a particular configuration of charges in a carrier is adapted, the apparatus cannot be changed to accommodate different sized charges or positions of charges for a different or other operation. In such case, if a change is desired, a new carrier must be configured with new shaped charges and a new mounting pattern therein because the old one or previous one cannot be modified. Thus, the earlier devices involved one unique charge with a piece of material, either molded or machined, permanently attached to the charge for positioning and holding the charge in the carrier. This restriction resulted in a design that performed only in its unique geometric parameters, including charge stand off, gun clearance, angularity and vertical spacing of the charges and could not be easily modified to accommodate a different operation.
The present invention overcomes the disadvantages of the prior art by providing a universal adaptation concept involving a charge that is designed around several gun sizes (geometric parameters) and is further complemented with interchangeable adaptors or clips for holding the charge in a charge carrier in proper relationship with both the carrier and a firing cord. This universal adaptation concept obviates the requirement to store the most popular sizes of the shaped charges because the present design can cover all sizes of shaped charges in the inventory. This eliminates the requirement to inventory all different sizes of shaped charges, charge carriers and adaptor or clip assemblies for holding charges in the carrier in proper relationship with a firing cord. The unique universal design of the charge and the charge adaptor or clip includes the trapping of the detonating or firing cord, a lock-in position in both the radial and transverse directions, and the vertical support of the shaped charge. Previous designs either trapped the cord or held the charge so as to prevent its moving in one direction, but never provided both advantages. The present design uses a flat, washer-shaped collar or flange on each shaped charge housing regardless of size. This flat, washer-type collar has a slot or space formed under the collar for mating with the improved adaptor or clip. The clip includes a body portion having a slot at one end thereof for receiving the washer-type collar of the shaped charge to hold the shaped charge in position. A retainer is formed at the other end of the improved clip or adaptor for extending through a port in the housing of the gun carrier assembly for supporting the shaped charge.
In the preferred embodiment of the universal adaptor or clip, the retainer portion of the clip includes a body construction having a U-shaped cavity therein so as to enable the legs of the U to be pressed together for insertion into a port of the gun carrier, the body construction returning to the U-shape after being inserted into the port. The bottom portion of the U-shaped cavity holds the firing cord in an abutting relationship with the shaped charge to allow proper operation thereof.
The charge holding slot in the universal clip is self-locking to securely hold the charge. To enable the clip to be self-locking, the slot has an entry portion having a width slightly less than the diameter of the flat, washer-shaped collar requiring a press fit of the charge body into the entry portion of the clip slot. It also has a charge holding portion in the form of a portion of a circle greater than 180.degree., the diameter of the circle portion being slightly larger than the diameter of the flat, washer-shaped collar allowing a free fit of the charge body with the holding portion of the clip slot. This construction enables the flat, washer-shaped collar of the shaped charge to be pressure forced through the entry portion of the clip slot into the charge holding portion that is in the form of a portion of a circle. The charge is then securely held in a self-locking relationship and will not be released from the clip through any movement of the charge. However, the charge can be manually forced back out of the mounting clip through the entry portion of the slot if necessary.
With this particular construction, the bottom portion of the U-shaped cavity is positioned inside the gun container for holding the firing cord against the charge.
In an alternate embodiment of the present invention, the retainer portion of the clip extends through a given carrier port and includes an opening therein for receiving the firing cord from the outside of the gun carrier for holding the charge in place for firing. The retainer in the alternate embodiment is press fit in the port of the carrier.